The use of passive acoustical sensors is becoming increasingly present in the fields of object detection and perimeter monitoring. Such sensors can provide integral data on the specific properties of an object of interest useful for a variety of applications, including but not limited to: military threat detection, highway traffic monitoring, environmental monitoring, and critical infrastructure protection. Conventional sensors gather environmental data by receiving input signals and continuously performing wideband Fast Fourier Transform (FFT) analysis to determine if the wideband spectrum contains a set of frequencies unique to the monitored object. While FFT analysis can be temporally convenient, it is often energy inefficient due to the large excess of continuous calculations performed from analyzing unnecessary background noise. This leads to higher maintenance costs by frequently inspecting or replacing sensors every few months or fewer. Furthermore, most acoustic sensors are tuned to detect objects only for a particularized distance and must be recalibrated each time the sensor is moved, making unattended sensors of limited use.
For the reasons stated above and for other reasons stated below, it will become apparent to those skilled in the art upon reading and understanding the specification, there is a need for distance independent differential signature detection.